usbcore: make hcd_endpoint_disable wait for queue to drain
The inconsistent lock state problem in usbcore (the one that shows up
when an HCD is unloaded) comes down to two inter-related problems:
usb_rh_urb_dequeue() isn't set up to be called with interrupts
disabled.
hcd_endpoint_disable() doesn't wait for all URBs on the
endpoint's queue to complete.
The two problems are related because the one type of URB that isn't
likely to be complete when hcd_endpoint_disable() returns is a root-hub
URB. Right now usb_rh_urb_dequeue() waits for them to complete, and it
assumes interrupts are enabled so it can wait. But
hcd_endpoint_disable() calls it with interrupts disabled.
Now, it should be legal to unlink root-hub URBs with interrupts
disabled. The solution is to move the waiting into
hcd_endpoint_disable(), where it belongs. This patch (as754) does that.
It turns out to be completely safe to replace the del_timer_sync() with
a simple del_timer(). It doesn't matter if the timer routine is
running; hcd_root_hub_lock will synchronize the two threads and the
status URB will complete with an unlink error, as it should.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
1 file changed